Infinite retry with exponential backoff in Kotlin using co-routines

InfiniteRetry.kt

/**
 * Copyright 2018 C.J. Campo
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

import kotlinx.coroutines.experimental.delay
import java.util.concurrent.TimeUnit

suspend fun <T> infiniteRetry(
  maxWait: Long = 10,
  unit: TimeUnit = TimeUnit.SECONDS,
  factor: Double = 1.0,
  onError: (Attempt) -> Unit = {},
  task: suspend () -> T
): T {
  var attempt = 0L
  var wait = 0L
  while (true) {
    try {
      return task()
    } catch (e: Exception) {
      onError(Attempt(attempt, wait, e))
    }
    delay(wait)
    wait = computeWaitTime(factor, unit.toMillis(maxWait), attempt)
    ++attempt
  }
}

fun computeWaitTime(multiplier: Double, maxWait: Long, attempt: Long): Long {
  val exp = Math.pow(2.0, attempt.toDouble())
  val result = Math.round(multiplier * exp).coerceAtMost(maxWait)
  return if (result >= 0L) result else 0L
}

data class Attempt(val num: Long, val wait: Long, val e: Exception)

/*
 * Example usage:
 *
 * infiniteRetry(onError = { attempt: Attempt -> handleError(attempt, ...) }) {
 *   doSomething(...)
 * }
 *
 */

you may use delay from - import kotlinx.coroutines.delay